DESCRIPTION: (Adapted from applicant's abstract: Within the past year there have been encouraging results in the treatment of HIV-1 infection resulting from the combinatorial use of drugs targeted against HIV-1 encoded reverse transcriptase and protease. Multiple targeting based upon rational drug design has therefore proven to be an effective method for dramatically inhibiting viral infectivity. Despite the success of the combinatorial drug therapy, there are cautious optimism and concerns about viral resistance, potential toxicity from long term use of the drugs, and long lived viral reservoirs that fully justify further development and testing of other types of antiviral therapies. One form of antiviral therapy that is actively being pursued by a number of laboratories is gene therapy, whereby antiviral genes are permanently introduced into hematopoietic cells to ameliorate viral infectivity. Within the past year, several different gene therapy trials have been initiated. One class of reagents currently in phase 1 clinical trials is ribozymes, which are site-specific RNA cleaving agents. These RNA molecules can be engineered to cleave at hundreds of different sites along the length of the HIV genome, thereby providing a multiple drug targeting strategy. The proposed research extends and takes advantage of lessons learned from our ongoing research efforts with anti-HIV ribozymes. The overall goal of this program is the enhancement of intracellular efficacy of anti-HIV ribozymes by understanding and utilizing intracellular and viral encoded proteins and novel RNA expression strategies to facilitate ribozyme-target co-localization. Concurrent with studies for improving ribozyme efficacy, combinations or ribozyme-expression cassettes will be inserted into Adeno Associated Viral vectors and HIV based lentiviral vectors for transduction into CD34+ hematopoietic progenitor cells, and transfusion into a SCID-hu mouse model. In this system the effects of anti-HIV-1 ribozyme expression on CD34+ cell differentiation and HIV-1 infection will be evaluated. The studies proposed encompass the most comprehensive study of anti-HIV-1 ribozyme function and pre-clinical analyses of ribozymes model to date. The results from this program will greatly facilitate the effective use of ribozyme treatment for HIV-1 infection in a gene therapy setting.